I whipped up a quick table runner (about 36" x 9") for Corey's Granny last weekend, again using the Robert Kaufman jelly roll. I still have quite a bit of it left, too! Anyway, the backing is just some royal blue Kona cotton, and I put felt inside as the batting. You can't really see it in this horrible cell phone picture, but I quilted the top using big Xs across each of the four blocks.
Instead of binding (which I was too chicken to do on a project for an amazing quilter such as Granny!), I used piping. Granny thought that was very fun.
The only bummer about doing everything that way is that there isn't any neat quilting to show through on the plain backing. I suppose I could add the quilting after final assembly, but then I would have to deal with the ugly backstitches showing. I could also add a second layer of batting to the backing and quilt it separately before assembly. Ooh -- I'm definitely going to try that next time!